Process for manufacturing a packaging material

ABSTRACT

A process for manufacturing a packaging material having at least two films ( 12, 16 ) or foils ( 14 ) bonded together via at least one layer of adhesive ( 13,15 ) to give a multi-layer laminate ( 10 ), is such that the adhesive layers ( 13,15 ) are of an adhesive that cures under electron beam radiation, and the laminate ( 10 ) is radiated with electrons for the purpose of curing the adhesive. The laminate is particularly suitable for the manufacture of self-standing pouches, in particular for drinks. The production of the laminate using adhesives that cure under electron beam radiation leads to a significantly reduced throughput time and to a reduction in the emission of solvents when replacing solvent-based adhesives by electron beam curing adhesives.

The invention relates to a process for manufacturing a packagingmaterial having at least two films or foils bonded together into amultilayer laminate by means of at least one layer of adhesive, wherebythe adhesive layer/layers is/are cure-hardened. Also within the scope ofthe invention is a self-standing pouch made from the laminate.

Laminates for manufacturing self-standing pouches for drinks aremanufactured today in two steps using solvent-free adhesives and in onestep using solvent-based adhesives.

The solvent-free process is environmentally friendly, however, requirestwo production steps. In a first step an aluminium foil is bonded to aprinted polyethyleneterephthalate (PET) film which is coated with asolvent-free poly-urethane (PUR) adhesive. After a curing time ofseveral hours this pre-laminate can be bonded to a polyolefin-film usinga solvent-based or solvent-free PUR adhesive. The final structure is:RET-film/adhesive layer/aluminium foil/adhesive layer/polyolefin film.After the final curing over a period of several days, the final laminatecan be cut to size and dispatched to the customer. The throughput timefrom receipt of order to dispatch of the finished product dependsessentially on the time required for curing the PUR-adhesive

The object of the invention is to provide a process of the kinddescribed at the start by means of which the time required for curingthe adhesive needed for the laminate—and with that the throughput timecan be reduced in comparison with the adhesive curing time inconventional laminate manufacture.

That objective is achieved by way of the invention in treat at least oneadhesive layer is of an adhesive that can be cured using an electronbeam and the laminate is radiated with electrons for the purpose ofcuring the adhesive.

The application of an electron beam curable adhesive results in anincrease of the initial adhesion, the so called greentack, which couldnot be expected at once. Furthermore the application of an electron beamcurable adhesive results not only in an excellent adhesion againstplastic films but also against aluminium foils. In addition, analuminium foil forms a functional barrier for electron beam curableadhesives, which is important with packaging for food, in particularbeverages.

The radiation curing of plastics that can be cured with an electron beamtakes place in a fraction of a second on passing through a radiationstation, whereby the final bond strength has already been essentiallyachieved without an additional curing time when the laminate emergesfrom the radiation station and is coiled.

The advantage of manufacturing laminate using adhesives that can becured by means of electron beam radiation is not only the much reducedthroughput time, but also in the reduction of solvent emissions issolvent based adhesives can be replaced by adhesives that can be curedusing an electron beam.

A preferred laminate exhibits three films or foils and two adhesivelayers, whereby one of the adhesive layers or both adhesive layersis/are of the electron beam curing type of adhesive.

If only one of the adhesive layers is curable with an electron beam, asolvent based or solvent-free PUR-adhesive is used by way of preferencefor the second adhesive layer.

A preferred laminate exhibits the following structure: PET film/firstadhesive layer of electron beam curable adhesive/aluminium foil/secondadhesive layer of an electron beam curable adhesive/polyolefin film.

If only one of the two adhesive layers is of an electron beam curableadhesive, a further preferred laminate exhibits the following structure:PET film/first adhesive layer of electron beam curableadhesive/aluminium foil/second adhesive layer of a solvent based orsolvent-free PUR adhesive/polyolefin film or PET film/first adhesivelayer of a solvent based or solvent-free PUR adhesive/aluminiumfoil/second adhesive layer of an electron beam curableadhesive/polyolefin film

Preferred polyolefin films are sealable films of polyethylene (PE) orpolypropylene (PP). For applications involving sterilisation or hightemperature cooking, PP is preferable because of its ability towithstand high thermal loads.

The PET film may exhibit printing on it. The printing is preferablyprovided as counterprint on the side coated with adhesive.

The electron beam curable adhesive is preferably an adhesive on anacrylate basis.

The adhesive on an acrylate basis may contain monomers, oligomers ormixtures of monomers and oligimers as the basis. Examples of monomersare mono, di- and multifunctional acrylates such as phosphoric acidester acrylates, hydroxy-acrylates, carboxy-acrylates, amino-acrylates,acrylic acid and acrylamide. Examples of oligomers are epoxy-acrylates,urethane-acrylates, polyester-acrylates and silicon-acrylates. Themonomers and oligomers mentioned are either available commercially orcan be manufactured by routine methods. The term “acrylate” (or “acryl”)used here also includes “methacrylate” (or “methacryl”, whereby theacrylates are preferred.

The laminate manufactured according to the invention is particularlysuitable for manufacturing self-standing pouches, in particular such fordrinks. Preferred is at least for the film of the laminate forming theoutside of the pouch to be laminated using an adhesive layer that can becured using an electron beam.

Further advantages, features and details of the invention are revealedin the following description of preferred exemplified embodiments andwith the aid of the drawing which shows schematically in

FIG. 1 cross-section through a laminated packaging film;

FIG. 2 manufacture of a pre-laminated partial film of the packaging filmshown in FIG. 1;

FIG. 3 manufacture of the packaging film in FIG. 1 from thepre-laminated partial film in FIG. 2;

FIG. 4 manufacture of the packaging film in FIG. 1 by triple lamination.

FIG. 1 shows a packaging film 10 for manufacturing self-standing pouchesfor drinks featuring a printed PET film 12 representing the outer side,an aluminium foil 14 as barrier layer and a sealable PE or PP film 16representing the inner side. The PET film 12 is permanently bonded tothe aluminium foil 14 by way of a first adhesive layer 13 and thealuminium foil 14 to the sealing film 16 by way of a second adhesivelayer 15. In a typical packaging film 10 the thickness of the PET filmis e.g. 12 μm, the thickness of the aluminium foil 8-10 μm and thethickness of the sealing layer 90-100 μm.

FIG. 2 shows the manufacture of a partial film A comprising PET film 12,adhesive layer 13 and aluminium foil 14. The printed PET film 12 isuncoiled from a first spool 18 in strip form an continuously coated withadhesive 13. The aluminium foil 14 is uncoiled in strip form from asecond spool 20 and fed to the PET film 12 coated with adhesive 13 andlaminated to this to a partial film A. The partial film A is passedthrough a radiation station 22 in which the adhesive layer 13 is curedby electron beam radiation within a fraction of a second. After leavingthe radiation station 22, the partial film A is coiled onto a thirdspool 24.

In a further production step, shown in FIG. 3, the sealing film 16 isuncoiled from a fourth spool 26 and continuously coated with adhesive15. The partial film A is fed from the third spool in strip form and fedto the sealing film 16 coated with adhesive 15 and laminatedcontinuously to this to yield the packaging film 10. The packaging filmpasses through a radiation station 28 in which the adhesive layer 15 iscured by electron beam radiation within a fraction of a second. Onleaving the radiation station 22 the packaging film 10 is coiled onto afifth spool 30.

The second adhesive layer 15 does not necessarily have to be an electronbeam curing adhesive. Instead, it may e.g. be a conventional PURadhesive. In that case the curing station 28 is omitted. The longercuring time required for the PUR adhesive has no influence on theprocess for producing the composite film 10 and simply requires aminimum storage time until it is processed further.

Another version of the manufacturing process—not shown in the drawing—issuch that first a partial film B comprising sealing film 16, adhesivelayer 15 and aluminium foil 14 is produced. The sealing film 16 isuncoiled from a first spool and Continuously coated with adhesive 15.The aluminium foil is fed to the sealing film 16 which is coated withadhesive 15 and laminated to this to give a partial film B. The partialfilm B passes through a radiation station in which the adhesive a layer15 is cured within a fraction of a second. After leaving the radiationstation, the partial film is coiled onto a third spool.

In a further step the printed PET film 12 is uncoiled from a fourthspool and coated continuously with adhesive 13. The partial film B isfed from the third spool to the PET film 12 coated with adhesive 13 andlaminated in a continuous manner to yield the packaging film 10. Thepackaging film 10 passes through a radiation station in which theadhesive layer 12 is cured by electron beam curing within a fraction ofa second. On leaving the radiation station the packaging film 10 iscoiled onto a fifth spool.

The first adhesive layer 13 does not necessarily have to be an electronbeam curing adhesive. Instead, it may e.g. be a conventional PURadhesive. In that case of course the radiation station is omitted. Thelonger curing time required by the PUR adhesive has no influence on theprocess for manufacturing the composite film 10 and requires simply aminimum storage time to be observed until further processing.

In a first way of manufacturing the threefold lamination shown in FIG.4, the production of the packaging film 10 takes place by bringingtogether the PET film 12, the aluminium foil 14 and the sealing film 16and adhesively bonding via the two adhesive layers 13, 15 in one singlepass. The printed PET film 12 is uncoiled from a first spool 32 andcoated continuously with adhesive 13. The aluminium foil 14 is fed instrip form from a second spool 34 to the PET film 12 coated withadhesive 13 and laminated continuously to this to yield partial film A.The sealing film 16 is uncoiled from a third spool 36 and coatedcontinuously with adhesive 15, fed in strip form to the partial film Aand laminated to it in a continuous manner yielding the packaging film10. The sealing film 16 is uncoiled from a third spool 36 and coatedwith (adhesive 15, fed in strip form to the partial film A and laminatedto it in a continuous manner yielding the packaging film 10. Thepackaging film 10 passes through a radiation station 38 with adequatecapacity enabling both adhesive layers 13, 15 to be cured by electronbeam radiation within a fraction of a second in one single pass. Onleaving the radiation station 38 the packaging film 10 is coiled onto afourth spool 40.

In a second way of manufacturing the threefold lamination shown in FIG.5, the production of the packaging film 10 takes place the same way asthe production shown in FIG. 4 by bringing together the PET film 12, thealuminium foil 14 and the sealing film 16 and adhesively bonding via thetwo adhesive layers 13,15 in one single pass. The aluminium foil 14 isuncoiled from a first spool 42 and coated continuously with adhesive 15at a first adhesive application station 17. The sealing film 16 is fedin strip form from a second spool 44 to the aluminium foil 14 coatedwith adhesive 15 and laminated continuously to this to yield partialfilm B. The partial film B passes through a first radiation station 50with adequate capacity enabling the adhesive layer 15 to be cured byelectron beam radiation within a fraction of a second. The PET film 12is uncoiled from a third spool 46 and coated continuously with adhesive13 at a second adhesive application station 19, fed in strip form to thepartial film B on leaving the first radiation station 50 and laminatedto it in a continuous manner yielding the packaging film 10. Thepackaging film 10 passes through a second radiation station 52 withadequate capacity enabling also the adhesive layer 13 to be cured byelectron beam radiation within a fraction of a second. On leaving theradiation station 52 the packaging film 10 is coiled onto a fourth spool48.

Immediately after coiling onto the spool 40, 48 the packaging film 10with fully cured adhesive layers 13, 15 is divided on a slitting lineinto commercially required breadths ready for dispatch.

It is self-evident that, on bonding the films or foils in the abovelaminating processes, the adhesive may also be deposited on the otherfilms or foils mentioned in the examples.

1. A process for manufacturing a packaging material having at least twofilms (12, 16) or foils (14) bonded together via at least one layer ofadhesive to give a multi-layer laminate (10), whereby the adhesivelayer/layers (13,15) is/are cured, at least one adhesive layer (13) isof an electron beam curable adhesive and the laminate (10) is radiatedwith electrons for the purpose of curing the adhesive.
 2. The processaccording to claim 1, wherein the laminate (10) exhibits three films(12,16) or foils (14) and two adhesive layers (13,15).
 3. The processaccording to claim 2, wherein one of the adhesive layers (13) is anadhesive that cures under electron beam radiation.
 4. The processaccording to claim 2, wherein both adhesive layers (13,15) are anadhesive that cures under electron beam radiation.
 5. The processaccording to claim 3, wherein the first adhesive layer (13) is anadhesive that cures under electron beam radiation and the secondadhesive layer (15) is a solvent-based or solvent-free PUR adhesive. 6.The process according to claim 4, wherein the laminate (10) exhibits thefollowing structure: PET film (12)/first adhesive layer of an electronbeam curing adhesive (13)/aluminum foil (14)/second adhesive layer of anelectron beam curing adhesive (15)/polyolefin film (16).
 7. The processaccording to claim 5, wherein the laminate (10) exhibits the followingstructure: PET film (12)/first adhesive layer of an electron beam curingadhesive (13)/aluminum foil (14)/second adhesive film (15) of asolvent-based or solvent-free PUR adhesive/polyolefin film (16).
 8. Theprocess according to claim 5, wherein the laminate exhibits thefollowing structure: PET film (12)/first adhesive layer of asolvent-based or solvent-free PUR adhesive (13)/aluminum foil(14)/second adhesive layer of an electron beam curing adhesive(15)/polyolefin film (16).
 9. The process according to claim 8, whereinthe PET film (12) exhibits printing on the side coated with adhesive.10. The process according to claim 9, wherein the polyolefin film is aPE or PP film.
 11. The process according to claim 10, wherein theelectron beam curing adhesive is an acrylate-based adhesive.
 12. Aself-standing pouch manufactured from a laminate (10) utilizing theprocess according to claim
 10. 13. A self-standing pouch manufacturedfrom a laminate (10) utilizing the process according to claim 10,wherein at least film (12) of the laminate (10) forming the outside ofthe pouch is laminated via an adhesive layer (13) that cures underelectron beam radiation.
 14. The self-standing pouch according to claim13, wherein the adhesive that cures under electron beam radiation is anacrylate-based adhesive.
 15. The process according to claim 6, whereinthe PET film (12) exhibits printing on the side coated with adhesive.16. The process according to claim 6, wherein the polyolefin film is aPE or PP film.
 17. The process according to claim 1, wherein theelectron beam curing adhesive is an acrylate-based adhesive.
 18. Theself-standing pouch manufactured from a laminate (10) utilizing theprocess according to claim
 1. 19. The self-standing pouch manufacturedfrom a laminate (10) using the process according to claim 2, wherein atleast film (12) of the laminate (10) forming the outside of the pouch islaminated via an adhesive layer (13) that cures under electron beamradiation.
 20. The self-standing pouch according to claim 19, whereinthe adhesive that cures under electron beam radiation is anacrylate-based adhesive.
 21. The self-standing pouch according to claim12, wherein the adhesive that cures under electron beam radiation is anacrylate-based adhesive.
 22. The self-standing pouch according to claim18, wherein the adhesive that cures under electron beam radiation is anacrylate-based adhesive.